HISTORY OF DERKYFIELD. 37 



round in the cavity, thus reinforcing the labor of the water. But 

 true pot-holes are so unlike any other rock excavations that they 

 can never be confounded. Their cylindrical form and vertical 

 direction, as well as their peculiar situation, preclude any but a 

 modified acceptance of the theory of Bouve. 



One pothole or "giants' kettle," described by Bouve as in the 

 "form of a cylinder," is sixteen feet deep by five broad. An- 

 other has a depth of about forty feet and a diameter of eight to 

 twelve. Much more remarkable than either is his account of 

 two others, found near Archbald, Pennsylvania, which we quote : 

 "The Archbald pot-holes are one thousand feet apart and were 

 both discovered in coal-mining, their bottoms being in the coal 

 bed. When the drift filling them was cleared out, one was found 

 to be thirty-eight feet deep, with a diameter of about fifteen feet 

 at the bottom, increasing to a maximum of forty-two feet and a 

 minimum of twenty-four feet across its top ; and the second, the 

 diameter of which is not definitely noted, was about fifty feet 

 deep in rock, with a covering of about fifteen feet of drift." 



In his remarkable work previously quoted, Prof. Wright gives 

 this: " On the water-parting between the Merrimack and the 

 Connecticut, there is to be found the dry bed of a river which 

 for a time flowed through a pass from the Connecticut valley 

 into the Merrimack, which is now five hundred feet above the 

 valleys. Here, upon this mountain axis in central New Hamp- 

 shire, nine hundred feet above the sea, are numerous and large 

 water-worn circular cavities in the rock, technically known as 

 pot-holes, such as are formed in shallow rapids, wherever gravel 

 and pebbles become lodged, first, in some natural slight depress- 

 ion, and then, through the whirling motion given them by the 

 running water, these continue to wear a symmetrical depression 

 so long as the supply of water continues, or until a channel has 

 been cut through. Pot-holes may be seen in the rapids of almost 

 any rocky stream, with the gravel and pebbles, which do the im- 

 mediate work when set in motion, still partially filling them. 



